Conventionally, there is known a hydraulic pressure control device for an automatic transmission which is a continuously variable transmission is a single pressure regulation (a line pressure=a secondary pressure), and which is configured to perform an oil vibration countermeasure to vary a feedback amount of a feedback control when an oil vibration is generated (for example, a patent document).
Recently, there is a continuously variable transmission which is a both pressure regulating type (including pressure regulating valves arranged to regulate, respectively, a primary pressure and a secondary pressure, based on a line pressure which is a source pressure).
In this continuously variable transmission which is the both pressure regulating type, in a case where the line pressure is greater than the secondary pressure, the actual secondary pressure is vibrated in some cases. That is, the oil vibration is generated. In this case, it is conceivable to decrease the oil vibration by increasing the line pressure to be greater than the hydraulic pressure generated before the oil vibration (the pressure difference between the line pressure and the secondary pressure is further increased).
On the other hand, when the auxiliary transmission is shifted, a transmitting path of the power from a traveling drive source to a driving wheel is varied. Accordingly, the oil vibration generated before the shift maybe converged by the shift (the oil vibration generated before the shift may be generated in the transmitting path after the shift). In a case where the oil vibration is converged (decreased), it is unnecessary to increase the line pressure. The fuel consumption is deteriorated in a case where the high line pressure is maintained.
In this way, when the auxiliary transmission mechanism is shifted in a state where the line pressure is increased, it is necessary to decrease the increased line pressure. There is a room for improvement about when the increased line pressure is decreased.